Conductivity-based sensory devices built on electrically conducting polymers (ECPs) offer great promise for the detection of a wide variety of analytes. They provide a greater current output compared to the traditional amperometry-based devices. Traditionally, intrinsic conductivity of polymers can be increased or reduced by a variety of molecular mechanisms upon analyte binding, including analyte-induced reductions in conjugation length and segmental energy matching/mismatching from adjacent redox-active sites. The difference in conductivity of a typical ECP between its non-conductive and conductive states is commonly 4-5 orders of magnitude. Therefore, the conductimetric response is very attractive for sensor applications.
A disadvantage of many conventional ECPs is that they are somewhat unstable in water, and generally have limited resistance to environmental conditions. Also, they possess relatively high onset potential and narrow conductive window. Further, these ECPs rely on conductivity difference for detections and sensor applications. However, these differences are not always sufficiently large to allow for ultrasensitive detection.